The present invention relates to article transport methods and to article transport apparatuses provided with a plurality of article transporting vehicles that are arranged so as to pass through a plurality of article transferring locations and that run along a path having a first end and a second end, and control means that controls the movement of the plurality of article transporting vehicles.
Such article transport apparatuses can be employed in automated warehouses, for example. The control means selects an article transporting vehicle for the transport process based on sequentially generated transport request data and moves the article transport vehicle for transport that has been selected to a target article transferring location, and by repeating this transport process each time transport request data is generated using any one of a plurality of article transporting vehicles, transports articles between a plurality of article transferring locations.
In such article transport apparatuses, it is important that this transport process is performed using a plurality of article transporting vehicles while avoiding collisions among article transporting vehicles.
Conventionally, apparatuses including a run-capable range that includes a plurality of article transferring locations into which only one of two article transporting vehicles can enter is set in advance at both ends of a path, a shared range that allows two article transporting vehicles to enter at different times also is set in advance in a center portion of the path, and control means that performs control such that, regardless of whether or not an article transporting vehicle is currently carrying out the transport process, the article transporting vehicle for the transport process that has been selected is transported to a target article transferring location in such a manner that the range in which that article transporting vehicle that has been selected for transport based on the transport request data does not interfere with the other run-capable ranges have been proposed (see JP 2002-175117A).
More specifically, the control means selects one of the two article transporting vehicles as the article transporting vehicle for a transport process based on which run-capable range the target article transferring is located in, for example, and moves the article transporting vehicle for transport to the target article transferring location in such a manner that the run-capable range of the selected article transporting vehicle does not interfere with the run-capable range of the remaining vehicle.
The control means is configured such that if it is to move an article transporting vehicle for the transport process into the shared range, then it moves the article transporting vehicle that is already in the shared range out of the shared range, or keeps the article transporting vehicle for transport on standby outside the shared range until the article transporting vehicle inside the shared range moves out of the shared range, thereby keeping the two article transporting vehicles from entering the shared range at the same time.
Since one condition of this conventional article transport apparatus is that the run range of the article transporting vehicle selected for a transport process based on transport request data does not interfere with other run-capable ranges, there is a large range over which this interference may occur, and this limits the size of the run range of the article transporting vehicle selected for transport based on the transport request data and leads to the possibility that articles may not be efficiently transported by the plurality of article transporting vehicles. That is to say, since the run-capable ranges set in advance include a plurality of article transferring locations, the run capable ranges also include ranges in which the article transporting vehicle being moved cannot run.
Consequently, when transport request data is generated at a time when one article transporting vehicle that is performing transport processing is present, the remaining vehicle can only run in a small run range, and thus the remaining article transporting vehicle cannot perform transport and it is not possible for the plurality of article transporting vehicles to efficiently transport articles.
The present invention was arrived at in light of these problems, and it is an object thereof to provide an article transport apparatus and an article transport method that can efficiently transport articles using a plurality of article transporting vehicles.